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Dear experts,
In the context of the BIDS transforms extension and the ".x5" format we chatted about in the workshop we made in March at MIT, we are addressing the following question.
We have a sphere of fsLR coordinates in fsaverage space (e.g., https://github.com/Washington-University/HCPpipelines/blob/master/global/tem... - but the question extends to the right hemisphere and also resolutions other than 59k). We want to expand this sphere to the fsaverage's white surface (lh.white, in this example). Since coordinates on the fsLR sphere don't match any of fsaverage{,3,4,5,6}'s coordinates, we wonder whether FreeSurfer stores somewhere/somehow the analytical transform of this mapping. In other words, how one would map arbitrary coordinates on the surface to a particular fsaverage's white (or midthickness, or pial, etc.) surface.
Otherwise, I guess I would pick fsaverage's surfaces (i.e., 7th degree icosahedron), and interpolate the displacement vectors that start at each sample on the surface and end at the corresponding location of that vertex index of the destination surface (lh.white for the example above).
Is there any tool that actually does the _inverse transform of the surface-to-sphere mapping_?
Thanks very much.
Regards, Oscar